YouTube often removes videos. Especially if these are super popular videos. I.e. Madonna - Celebration
So I just added similar videos search based on keywords from the title (if such is present). It works the same way as similar video search when the video is unembeddable, i.e. Roxette - Spending My Time, which, unfortunately does not bring any more versions of "Spending My Time", but in theory, it could, if such were available.